1. Field of the Invention
This invention relates to mixing devices for mixing and dispensing reactive chemical streams. More particularly, this invention relates to a modular mixing device that provides flexibility to enable the device to be reconfigured to accurately mix and dispense different reactive input streams as a properly mixed end product.
2. Description of the Background of the Invention
Reactive chemical compositions, such as polyurethane foam compositions are well known in the art. These compositions typically are combined shortly before use by combining or intimately mixing the two reactive chemical components. For polyurethane foam, the two components are a polyol and an isocyanate. These two materials are highly reactive and readily react at various temperatures to form a foam material with a wide range of physical properties. Typical uses for these polyurethane foams include thermal insulation, floatation, cushioning for packaging, and the like. Most polyurethane foams used for insulation, floatation and packaging are rigid foams. These rigid polyurethane foams are formed when the polyol and isocyanate components are mixed. Upon mixture, the reaction commences and a voluminous foam is formed as the reaction products and/or optional blowing agents build volume within the reactive foam structure. As the reaction continues the foam hardens or becomes rigid.
Within the insulation industry, the two components are stored in separate drums or containers and are mixed just prior to the foam being placed within a structure to be insulated. In a manufacturing setting, this can include refrigerator or freezer walls, cooling chests, storage units and the like. In this setting, a dispensing device, often hand held, is used to both mix and dispense the foam into the cavity to be insulated. There have been numerous hand held devices, such as that disclosed in U.S. Pat. No. 5,246,143, to mix and dispense reactive chemical streams such as the two part streams used to make polyurethane foam in situ. The device disclosed in this patent mixed two streams in a valve cartridge that is removable and can be disposed if the cartridge becomes fouled by reacted polymer.
In the past, chemical manufacturers produced foam insulation products as two premixed component foam compositions. These premixed components included the polyol component and the isocyanate component blended with various additives such as catalyst packages, blowing agents, curing agents, modifiers, colorants, and the like.
Recently, there has been a trend by chemical manufacturers to offer the end users incomplete pre-blend formulas intended for special applications. These pre-blend formulations typically do not contain the blowing agent, in part because of the special shipping and handling requirements for compositions containing blowing agents. In this case, the manufacturer provides components and pre-blends with instructions on the proper formulation of these materials to achieve specific results. As a result, the end users must now mix and blend the necessary blowing agents with one of the primary chemical components, typically the polyol, often requiring a significant investment in equipment, and engineering time. At present, there is no convenient way for an end user to custom blend these materials at the dispensing device to achieve custom individualized results.
In the past, the devices that were designed to mix and dispense these two part reactive compositions did not include the ability to mix various additive and additive packages into one or both of the main reactive chemical streams These prior devices do not have the flexibility to handle the task of custom mixing various input streams to enable a manufacturer or installer to easily prepare two part components systems in situ from the individual chemical components that are currently available from and usually sold by chemical manufacturers. Also, because these devices were developed to meet the needs based on prior complete and fully blended systems, they may not be able to handle the needs of a user that must accurately blend multiple components as they are being used and may need to adjust that blend during the dispensing process.
Depending on the specific type of foam to be produced, the dispensing devices must be able to adapt to these changing needs. For instance, a foam that is placed within a cavity may need a device that includes an extension of the exit tip or port so that the foam will be unconfined only after it enters the void volume and thereafter will expand to properly fill the entire void volume. In other applications, the foam will be sprayed on the exterior of a shape. In this instance, the foam components will be mixed with a carrier stream such as air as the foam components are sprayed onto the surface to be coated. In this instance, the foam will be formed either as the foam components are first dispensed or will expand once the components are deposited on the coating surface.